1. Field of the Invention
The present invention relates to mailpiece inserter systems, and, in particular, to a method and apparatus for detecting the thickness of mailpieces being produced in an inserter system in order to detect and reduce possible mailpiece integrity breaches.
2. Description of the Related Art
Inserter systems are typically used by organizations such as banks, insurance companies, and utility companies for producing a large volume of specific mailings where the contents of each mailpiece are directed to a particular addressee. In many respects, a typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (e.g., enclosures and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process sheets until a finished mailpiece is produced. Typically, inserter systems prepare mailpieces by gathering collations of documents on a conveyer. The collations are then transported on the conveyer to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing, such as automated closing and sealing of the envelopes, weighing of the envelopes, applying postage to the envelopes, and finally sorting and stacking the envelopes.
Mailpiece integrity is a significant concern for users of inserter systems and refers to the correct mailpiece contents being present in an envelope before it enters the mail stream. Many users, particularly in the financial services sector, require and demand extremely high mailpiece integrity levels.
Manufacturers of inserter systems thus make significant efforts to improve hardware and machine control software to reduce the possibility of integrity breaches. One method of reducing the possibility of integrity breaches that has been developed involves measuring the thickness of each mailpiece during production and comparing it to an expected thickness for the mailpiece, wherein the expected thickness is derived in advance from the proper contents for the mailpiece. Mailpieces that fail this integrity check can be diverted from the mail stream for further investigation.
In one conventional system, thickness measurement data is captured from a moving mailpiece during the application of a compressive force on the mailpiece by a detector that is kept in contact with the paper path at all times. This causes two negative effects. First, when an oncoming mailpiece contacts the detector, the impact force drives the detector in a direction that is perpendicular to the paper path direction and causes the detector to oscillate on the mailpiece before an accurate thickness measurement can be taken. Second, mailpieces contain ridges or edges due to the contents, envelope flaps, windows, and/or side seams thereof, and when the detecting roller contacts these thickness variations, similar but smaller oscillations and settling time are introduced before an accurate thickness measurement can be made. Both of these effects increase the required contact zone length for the mailpiece, which represents the minimum length of the mailpiece that must be of substantially constant thickness for an accurate thickness measurement to be made.